PERFORMANCE ANALYSIS OF SIMPLE-T AND 3DHELICAL PASSIVE MICROMIXERS WITH NEWTONIAN AND NON-NEWTONIAN FLUID

Abstract

Mixing at micro-scales is purely governed by the diffusion mass transport phenomenon, which is a time-consuming process requiring a prolonged length of the microchannel to obtain desired results. The present study proposes a novel three-dimensional helical micromixer (TDHM) with a rectangular cross-section to achieve splendid mixing performance within a short distance contrary to the simple T-micromixer (STM). A thorough numerical investigation of mixing performance and fluid flow patterns have been conducted using the continuity, species transport, and the Navier-stokes equations with Newtonian and non-Newtonian fluid at a wide range of Reynolds number (0.2~320) and mass flow rate (0.00005 kg/hr~0.091 Kg/hr), respectively and a comparison between the results of STM and TDHM are presented. Blood is selected as the Non-Newtonian fluid and its rheological characteristics are numerically captured by implementing the Carreau-Yasuda model, whereas water is used to study mixing with the Newtonian fluid. For the same mixing length of STM and TDHM i.e. 3000 microns it is found that at Re = 2, the mixing index of TDHM is 40. 5% more than that of the STM with water as the working fluid while for blood it is 34.3% and it is seen that TDHM performs better than the STM at all the mass loadings. Once the results for the same mixing lengths are computed, another study is conducted fixing the axial lengths of STM and TDHM. Complete mixing (97.5%) is achieved for Newtonian fluid at Re=320 whereas the minimum efficiency observed is 74.3 % at Re = 66. Although for Non-Newtonian fluid (Blood) the conventional STM gives poor mixing with increased mass flow rate. However, TDHM furnish splendid mixing with 97% efficiency at the lowest mass flow rate of blood (ṁ ) considered in the study, i.e. 0.00005 Kg/hr and 73.6 % at ṁ =0.091 Kg/hr. Therefore, it was concluded that the TDHM gives much better performance at much less axial distance than that of the STM at all values of the flow rates considered in the study making it an effective choice to be utilized for various biomedical, chemical, and biochemical applications.